WO2017187733A1

WO2017187733A1 - Current sensor

Info

Publication number: WO2017187733A1
Application number: PCT/JP2017/006352
Authority: WO
Inventors: 田村　学; 英一郎松山
Original assignee: アルプス電気株式会社
Priority date: 2016-04-27
Filing date: 2017-02-21
Publication date: 2017-11-02

Abstract

The present invention is provided with: a first bus bar 10 linearly extending between two end sections E11 and E12 wherein currents flow; a second bus bar 20 that is bent between two end sections E21 and E22 wherein currents flow; and magnetic sensors SA and SB that detect magnetic fields generated due to a current flowing in the second bus bar 20. The end section E11 of the first bus bar 10, and the end section E21 of the second bus bar 20 are in contact with each other, and are electrically connected to each other, and the end section E12 of the first bus bar 10, and the end section E22 of the second bus bar 20 are in contact with each other, and are electrically connected to each other. The magnetic sensors SA and SB respectively detect the magnetic fields in the Y direction parallel to the extending direction of the first bus bar 10.

Description

Current sensor

The present invention relates to a current sensor that detects a current based on a magnetic field, and more particularly to a current sensor that can detect a relatively large current from a shunt current based on a magnetic field of a shunt current.

When a large current exceeding the detection range of the current sensor is detected, it is generally performed that the current shunted from the current to be detected is detected by the current sensor. Patent Literature 1 below describes a bus bar structure in which a shunt bus bar is connected in parallel to a bus bar that is a current detection target.

JP-A-9-93711

However, in the bus bar structure described in Patent Document 1, two bus bars to which a current to be detected is divided are arranged substantially in parallel. Therefore, the magnetic field generated by the currents flowing through these bus bars has components in directions parallel to each other. It becomes easy to do. When a magnetic field is detected using a magnetoelectric conversion element (GMR element, etc.) having a specific sensitivity direction, if the sensitivity direction is matched to the direction of the magnetic field due to the current of one bus bar, the magnetic field due to the current of the other bus bar is also detected. End up. That is, there is a disadvantage that the detection result of the magnetic field due to the current diverted to one bus bar is affected by the magnetic field due to the current diverted to the other bus bar, and the current detection accuracy is lowered.

In order to reduce the influence of the magnetic field due to the current diverted to the other bus bar, it may be possible to provide a magnetic shield or a magnetic field detection core, but this increases the number of components and increases the size. There is a disadvantage.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a current sensor that can accurately detect a current based on a magnetic field of a shunt current.

The current sensor of the present invention flows through the first bus bar extending linearly between two ends where current flows, the second bus bar bent between the two ends where current flows, and the second bus bar. A magnetic sensor for detecting a magnetic field due to an electric current is provided. The one end of the first bus bar and the one end of the second bus bar are in contact with each other and are electrically connected, and the other end of the first bus bar and the other end of the second bus bar. And are in contact with each other. The magnetic sensor detects a magnetic field in a direction parallel to the extending direction of the first bus bar.

According to this configuration, since the first bus bar and the second bus bar are in contact with each other at the two end portions and are conductive, at least a part of the second bus bar bent between the two end portions. Current flows in a direction that is not parallel to the extending direction of the first bus bar extending linearly between the two ends. Thereby, since the magnetic field due to the current flowing in at least a part of the second bus bar has a component parallel to the extending direction of the first bus bar, this can be detected by the magnetic sensor. In addition, since the magnetic field due to the current flowing through the first bus bar is perpendicular to the extending direction of the first bus bar, it is difficult to be detected by the magnetic sensor. That is, the magnetic sensor mainly detects a magnetic field due to the current flowing through the second bus bar, and the detection result is hardly affected by the magnetic field due to the current flowing through the first bus bar.

Preferably, the current sensor includes a pair of the magnetic sensors disposed at a pair of places. The pair of places is a place where the magnetic field generated by the current of the second bus bar has a magnetic field component parallel to the extending direction of the first bus bar, and the magnetic field component of each other is a current flowing through the second bus bar. It is a place with a corresponding difference.

According to this configuration, the magnetic field component parallel to the extending direction of the first bus bar included in the magnetic field generated by the current of the second bus bar at the pair of locations has a difference corresponding to the current flowing through the second bus bar. Have. In the pair of magnetic sensors arranged at the pair of locations, a magnetic field parallel to the extending direction of the first bus bar is detected, respectively. Therefore, the magnetic field detected by the pair of magnetic sensors is applied to the second bus bar. There is a difference according to the flowing current. Therefore, the current flowing through the second bus bar can be detected based on the difference between the magnetic fields detected by the pair of magnetic sensors. Since the external magnetic field from a distant noise source becomes substantially equal at the pair of locations, it is difficult to affect the difference between the magnetic fields detected by the pair of magnetic sensors.

Preferably, the second bus bar extends linearly in a direction inclined with respect to the extending direction of the first bus bar from the bent portion to the two end portions from the bent portion. With two equal arms. The pair of magnetic sensors are disposed in a pair of locations that are symmetrical with respect to a virtual plane that passes through the bent portion and is perpendicular to the extending direction of the first bus bar, and currents flowing through the two arm portions. Detect the magnetic field due to.

According to this configuration, the magnetic field distribution due to the current flowing through the second bus bar is symmetric with respect to the virtual plane, and the magnetic fields parallel to the extending direction of the first bus bar are opposite to each other at the pair of locations. Therefore, the magnetic field detected by the pair of magnetic sensors has a difference corresponding to the current flowing through the second bus bar. Further, since the arm portion is inclined with respect to the extending direction of the first bus bar, the magnetic field due to the current flowing through the arm portion is not parallel to the extending direction of the first bus bar. Thereby, since the detection sensitivity of the magnetic field with respect to an electric current becomes low, a larger electric current can be detected.

Preferably, the second bus bar is provided between two bent portions, between the one bent portion and the one end portion, and between the other bent portion and the other end portion. And two arm portions extending linearly in a direction perpendicular to the extending direction of the first bus bar and parallel to each other, and a base portion provided between the two bent portions. The pair of magnetic sensors are disposed at a pair of locations that are plane-symmetric with respect to a virtual plane that passes through the center of the base in the extending direction of the first bus bar and is perpendicular to the extending direction. A magnetic field due to the current flowing through the arm is detected.

According to this configuration, the distribution of the magnetic field due to the current flowing through the second bus bar is symmetric with respect to the virtual plane. Therefore, of the magnetic field due to the current flowing through the second bus bar, the magnetic field components parallel to the extending direction of the first bus bar are opposite to each other in the pair of locations, and the magnitudes thereof are substantially equal. Therefore, the magnetic field detected by the pair of magnetic sensors has a difference corresponding to the current flowing through the second bus bar. Further, since the arm portion is perpendicular to the extending direction of the first bus bar, the magnetic field due to the current flowing through the arm portion is parallel to the extending direction of the first bus bar. Thereby, since the detection sensitivity of the magnetic field with respect to an electric current becomes high, the detection of a smaller electric current is attained.

Preferably, each of the first bus bars includes a plurality of plate-like conductors that extend linearly in the extending direction and are stacked in a direction perpendicular to the extending direction.

According to this configuration, by changing the number of stacked plate conductors in the first bus bar, it is possible to easily change the ratio of the diversion between the first bus bar and the second bus bar. . This makes it possible to easily change the current detection range.

Preferably, the currents flowing through each of the plurality of plate conductors are equal to each other, and the current flowing through one of the plate conductors is equal to the current flowing through the second bus bar.

According to this configuration, it is possible to change the current detection range to an integer multiple by changing the number of stacked plate conductors in the first bus bar.

Preferably, the plurality of plate-like conductors have the same planar shape as viewed from the stacking direction.

According to this configuration, even if the number of stacked plate-shaped conductors is increased, the size of the planar shape of the first bus bar viewed from the stacking direction does not change, so the size of the device is increased by expanding the current detection range. Is suppressed.

Preferably, the two end portions of the second bus bar are stacked on the plate-like conductor in the same direction as the stacking direction.

According to this configuration, even when the number of stacked plate conductors in the first bus bar is changed, the contact between the second bus bar and the first bus bar is stably ensured.

Preferably, the current sensor can connect the two end portions of the second bus bar and the plurality of plate conductors with screws. The two end portions of the second bus bar are respectively formed with through holes through which the screws are inserted in a direction parallel to the stacking direction. A through hole through which the screw is inserted is formed in each of the two end portions of the plate-like conductor in a direction parallel to the stacking direction.

According to this structure, since it becomes possible to overlap and connect another bus bar to the connecting portion between the second bus bar and the plurality of plate conductors by the screws, the number of stacked plate conductors increases. However, the connecting work is not complicated.

According to the present invention, the current can be detected with high accuracy based on the magnetic field of the shunt current.

It is a figure which shows an example of the current sensor which concerns on the 1st Embodiment of this invention. It is a figure which shows the state by which the bus-bar connected in parallel in the current sensor shown in FIG. 1 was decomposed | disassembled. It is a figure which shows an example of the attachment state of the current sensor shown in FIG. In the current sensor shown in FIG. 1, it is the figure which illustrated the direction of the magnetic field by the electric current which flows into a bus-bar. It is a figure which shows an example of a structure of a sensor part. It is a figure which shows an example of the current sensor which concerns on the 2nd Embodiment of this invention. It is a figure which shows the state by which the bus-bar connected in parallel in the current sensor shown in FIG. 6 was decomposed | disassembled. It is a figure which shows an example of the attachment state of the current sensor shown in FIG. FIG. 7 is a diagram illustrating the direction of a magnetic field due to a current flowing in a bus bar in the current sensor shown in FIG. 6.

<First Embodiment>
FIG. 1 is a diagram showing an example of a current sensor 1 according to the first embodiment of the present invention. A current sensor 1 shown in FIG. 1 includes a first bus bar 10 and a second bus bar 20 connected in parallel, and magnetic sensors SA and SB that detect a magnetic field (magnetic flux density) due to a current flowing through the second bus bar 20. Part 50.

As shown in FIG. 1, in this specification, three directions orthogonal to each other are assumed to be “X”, “Y”, and “Z”. Also, the opposite directions included in the X direction are “X1” and “X2”, the opposite directions included in the Y direction are “Y1” and “Y2”, and the opposite directions included in the Z direction are opposite to each other. The direction of “Z1” and “Z2”.

The first bus bar 10 has a shape extending linearly between two ends E11 and E12 through which current flows, thereby forming a linear current path. In the example of FIG. 1, the extending direction of the first bus bar 10 is the Y direction.

FIG. 2 is a diagram showing a state in which the bus bars (10, 20) connected in parallel in the current sensor 1 shown in FIG. 1 are disassembled. As shown in FIG. 2, the first bus bar 10 includes two plate-

like conductors

10A and 10B. The plate-

like conductors

10A and 10B are smaller in size (thickness) in the Z direction than in the X direction (width), and each extend linearly in the Y direction. The plate-

like conductors

10A and 10B are stacked in the Z direction as shown in FIG. That is, the surface on the Z2 side of the plate-like conductor 10A and the surface on the Z1 side of the plate-like conductor 10B are in contact.

1 and 2, the two plate-

like conductors

10A and 10B have the same planar shape when viewed from the Z direction (stacking direction). That is, the X-direction width and the Y-direction length of the plate-

like conductors

10A and 10B are equal. The width in the X direction of the plate-shaped conductor 10A is narrower in the middle portion than the two ends E11A and E12A, and the width in the X direction of the plate-shaped conductor 10B is also the two ends E11B, The middle part is narrower than E12B.

The second bus bar 20 has a bent shape between the two end portions E21 and E22 through which current flows, thereby forming a bent current path. In the example of FIG. 1, the second bus bar 20 has a bent portion 23 and two

arm portions

21 and 22. The bent portion 23 is located between the two end portions E21 and E22. The two end portions E21 and E22 extend linearly from the bent portion 23 to the two end portions E21 and E22 in a direction inclined with respect to the Y direction. The arm portion 21 extends linearly from the bent portion 23 to the end portion E21, and the arm portion 22 extends linearly from the bent portion 23 to the end portion E22. The

arm portions

21 and 22 each extend perpendicularly to the X direction and have substantially the same length in the extending direction.

Moreover, the 2nd bus bar 20 shown in FIG. 1 has the bending part 24 between the arm part 21 and the edge part E21, and has the bending part 25 between the arm part 22 and the edge part E22. Both the end E21 and the end E22 extend linearly in the Y direction.

In the current sensor 1 shown in FIG. 1, the end E11 of the first bus bar 10 and the end E21 of the second bus bar 20 are in contact with each other, and the end E12 of the first bus bar 10 and the end of the second bus bar 20 are connected. E22 contacts and conducts.

The two ends E21 and E22 of the second bus bar 20 are stacked on the plate conductor 10A in the same direction as the stack direction (Z direction) of the

plate conductors

10A and 10B. That is, the Z2 side surface of the end portion E21 of the second bus bar 20 and the Z1 side surface of the end portion E11A of the plate conductor 10A are in contact with each other, and the Z2 side surface of the end portion E22 of the second bus bar 20 and the plate conductor 10A. The Z1 side surface of the end E12A comes into contact. The second bus bar 20 is a plate-like conductor similar to the plate-

like conductors

10A and 10B, and the size (thickness) in the Z direction of the end portion E21 and the end portion E22 is smaller than the size (width) in the X direction.

In one example, substantially equal currents flow through the plate-like conductor 10A, the plate-like conductor 10B, and the second bus bar 20. That is, these conductors have approximately the same resistance value between the two ends where current flows. In these conductors, the width in the X direction, the thickness in the Z direction, the length of the current path, the area of the contact portion, etc. are set so that substantially equal currents flow.

FIG. 3 is a diagram showing an example of the attached state of the current sensor 1 shown in FIG. 1, and is a view of the X2 direction from the X1 side. As shown in the example of FIG. 3, the current sensor 1 according to the present embodiment can connect the two ends E21 and E22 of the second bus bar 20 and the

plate conductors

10A and 10B with screws (81, 83). is there. A through hole through which a screw (81, 83) is inserted in the Z direction is formed at each end of the second bus bar 20, the plate conductor 10A, and the plate conductor 10B. The second bus bar 20 has a through hole T21 at the end E21 and a through hole T22 at the end E22. The plate-like conductor 10A has a through hole T11A formed at the end E11A and a through hole T12A formed at the end E12A. The plate-like conductor 10B has a through hole T11B at the end E11B and a through hole T12B at the end E12B. A screw 81 is inserted through the through holes T21, T11A, and T11B, and a screw 83 is inserted through the through holes T22, T12A, and T12B. The nuts 82 and 84 are fastened to the tips of the

screws

81 and 83 inserted through the through holes, whereby the two ends E21 and E22 of the second bus bar 20 and the plate-

like conductors

10A and 10B are connected.

As shown in FIG. 3, the

screws

81 and 83 are used to connect the bus bars 101 and 102 through which the current to be detected flows and the current sensor 1. The end of the bus bar 101 has a through hole through which the screw 81 is inserted in the Z direction, and is fixed between the end E11B of the plate-like conductor 10B and the nut 82. The end of the bus bar 102 has a through hole through which the screw 83 is inserted in the Z direction, and is fixed between the end E12B of the plate-like conductor 10B and the nut 84.

The magnetic sensors SA and SB are sensors having high sensitivity to a magnetic field in a specific direction (sensitivity direction), and include a magnetoresistive effect element such as a GMR element. The sensitivity directions of the magnetic sensors SA and SB are directed in the Y direction so as to detect a magnetic field in the Y direction parallel to the extending direction of the first bus bar 10.

A pair of magnetic sensors SA and SB (hereinafter referred to as “a pair of magnetic sensors”) is disposed at a pair of locations. The pair of places are places where the magnetic field generated by the current of the second bus bar 20 has a magnetic field component in the Y direction parallel to the extending direction of the first bus bar 10, and the magnetic field components of each other are the second bus bar 20. It is a place with a difference according to the current flowing through. That is, in this pair of locations, when the current of the second bus bar 20 increases, the difference in the magnetic field component in the Y direction due to this current increases. Conversely, when the current of the second bus bar 20 is reduced, the difference in the magnetic field component in the Y direction due to this current is reduced.

In the example of FIG. 3, the pair of magnetic sensors (SA and SB) are arranged at a pair of locations that are plane-symmetric with respect to the virtual plane PL. The virtual plane PL is a plane that passes through the bent portion 23 and is perpendicular to the extending direction (Y direction) of the first bus bar 10. Since the first bus bar 10 and the second bus bar 20 have a symmetrical shape with respect to the virtual plane PL, the distribution of the magnetic field due to the current flowing through the first bus bar 10 and the second bus bar 20 is substantially symmetrical with respect to the virtual plane PL. It becomes. The pair of magnetic sensors (SA and SB) detect magnetic fields due to currents flowing through the two

arm portions

21 and 22 in a pair of locations that are plane-symmetric with respect to the virtual plane PL.

FIG. 4 is a diagram illustrating the direction of the magnetic field due to the current flowing through each bus bar (10, 20) in the current sensor 1 shown in FIG. In FIG. 4, “I1” indicates a current flowing through the first bus bar 10 (

plate conductors

10A and 10B), and “I2” indicates a current flowing through the second bus bar 20.

4, the magnetic sensor SA includes two magnetoresistive elements M1 and M2, and the magnetic sensor SB includes two magnetoresistive elements M3 and M4. The arrow in FIG. 4 represents the sensitivity direction, the sensitivity direction of the magnetoresistive effect elements M1 and M3 is the Y1 direction, and the sensitivity direction of the magnetoresistive effect elements M2 and M4 is the Y2 direction.

The magnetic field H21 generated by the current I2 flowing through the arm portion 21 at the location where the magnetic sensor SA (the magnetoresistive effect elements M1 and M2) is disposed, and the arm at the location where the magnetic sensor SB (the magnetoresistive effect elements M3 and M4) is disposed. The component in the Y direction is opposite to the magnetic field H22 generated by the current I2 flowing through the portion 22. For example, as shown in FIG. 4, when the current I2 flows from the Y2 side to the Y1 side, the magnetic field H21 has a magnetic field component in the Y1 direction, and the magnetic field H22 has a magnetic field component in the Y2 direction. Further, since the second bus bar 20 has a symmetrical shape with respect to the virtual plane PL, the magnetic field generated by the current I2 flowing through the second bus bar 20 is substantially symmetrical with respect to the virtual plane PL, and a pair of magnetic sensors The magnetic field strengths in (SA and SB) are almost equal. Therefore, in the pair of locations where the pair of magnetic sensors (SA and SB) are disposed, the magnetic field components in the Y direction of the magnetic field generated by the current I2 are opposite to each other, and the magnitudes thereof are approximately equal.

On the other hand, the magnetic field H1 due to the current I1 flowing through the first bus bar 10 is perpendicular to the Y direction and has almost no magnetic field component in the Y direction. Therefore, in the magnetic sensors SA and SB (magnetoresistance effect elements M1 to M4), the magnetic field H1 due to the current I1 is hardly detected.

The sensor unit 50 generates a detection signal indicating the detection result of the current I2 flowing through the second bus bar 20 based on the difference between the magnetic fields detected by the pair of magnetic sensors (SA and SB). In the example of FIG. 4, the sensor unit 50 includes a bridge circuit 51 that detects changes in the resistance values of the magnetoresistive elements M1 to M4. The bridge circuit 51 includes a half bridge composed of magnetoresistive elements M1 and M2 constituting the magnetic sensor SA, and a half bridge composed of magnetoresistive elements M2 and M4 constituting the magnetic sensor SB. In one half bridge (magnetic sensor SA), the magnetoresistive effect element M1 and the magnetoresistive effect element M2 are connected in series, and the power supply voltage VDD is applied to one end of the magnetoresistive effect element M1, and the magnetoresistive effect element One end of M2 is connected to the ground. In the other half bridge (magnetic sensor SB), the magnetoresistive effect element M3 and the magnetoresistive effect element M4 are connected in series, and the power supply voltage VDD is applied to one end of the magnetoresistive effect element M3. One end of M4 is connected to the ground. The bridge circuit 51 outputs a voltage Va at the midpoint of connection between the magnetoresistive elements M1 and M2, and outputs a voltage Vb at the midpoint of connection between the magnetoresistive elements M3 and M4.

The resistance value of the magnetoresistive effect element decreases as the magnetic field in the sensitivity direction increases. Therefore, as shown in FIG. 4, when the current I2 flowing from the Y2 side to the Y1 side increases (or when the current I2 flowing from the Y1 side to the Y2 side decreases), the resistance values of the magnetoresistive elements M1 and M4 are relatively And the resistance values of the magnetoresistive effect elements M2 and M3 become relatively large. Therefore, the voltage Va increases and the voltage Vb decreases. Conversely, when the current I2 flowing from the Y2 side to the Y1 side decreases (or when the current I2 flowing from the Y1 side to the Y2 side increases), the resistance values of the magnetoresistive effect elements M1 and M4 become relatively large, and the magnetic Since the resistance values of the resistance effect elements M2 and M3 are relatively small, the voltage Va decreases and the voltage Vb increases.

FIG. 5 is a diagram illustrating an example of the configuration of the sensor unit 50. The sensor unit 50 shown in the example of FIG. 5 includes a coil L, a coil drive circuit 52, a differential amplifier 53, and a resistor Rs in addition to the bridge circuit 51 described above.

The coil L generates a magnetic field for canceling the magnetic field in the Y direction generated at each position of the magnetoresistive effect elements M1 to M4 by the current I2 of the second bus bar 20. For example, as shown in FIG. 5, the coil L forms a current path CP1 extending in the Z direction in the vicinity of the magnetoresistive elements M1 and M2. When the current Ib flows through the current path CP1 in the Z2 direction, a magnetic field H51 in the Y2 direction is generated in the vicinity of the magnetoresistive elements M1 and M2. The magnetic field H51 cancels the magnetic field component in the Y1 direction generated at the position of the magnetoresistive effect elements M1 and M2 by the current I2. Similarly, the coil L forms a current path CP2 extending in the Z direction in the vicinity of the magnetoresistive elements M3 and M4. When the current Ib flows through the current path CP2 in the Z1 direction, a magnetic field H52 in the Y1 direction is generated in the vicinity of the magnetoresistive elements M3 and M4. This magnetic field H52 cancels the magnetic field component in the Y2 direction generated at the position of the magnetoresistive effect elements M3 and M4 by the current I2.

The coil drive circuit 52 causes a current Ib corresponding to the difference between the voltages Va and Vb of the bridge circuit 51 to flow through the coil L.

Suppose that the resistance values of the magnetoresistive elements M1 to M4 are substantially equal when the magnetic field is zero. In this case, when the current I2 of the second bus bar 20 becomes zero, the voltages Va and Vb become substantially equal. When the current I2 flows from the Y2 side to the Y1 side of the second bus bar 20, the resistance values of the magnetoresistive elements M1 to M4 change due to the magnetic field in the Y direction due to the current I2, and the voltage Va becomes higher than Vb. When voltage Va is higher than Vb, coil drive circuit 52 outputs current Ib so that current path CP1 flows in the Z2 direction and current path CP2 flows in the Z1 direction. The coil drive circuit 52 increases the current Ib as the difference between the voltages Va and Vb increases. In the vicinity of the magnetoresistive elements M1 to M4, the magnetic field in the Y direction generated by the current Ib of the coil L acts so as to cancel the magnetic field component in the Y direction generated by the current I2 of the second bus bar 20. Therefore, the rise of the voltage Va with respect to the voltage Vb is suppressed.

On the other hand, when the current I2 flows from the Y1 side to the Y2 side of the second bus bar 20, the voltage Va becomes lower than Vb, contrary to the above. When voltage Va is lower than Vb, coil drive circuit 52 outputs current Ib so that current path CP1 flows in the Z1 direction and current path CP2 flows in the Z2 direction. The coil drive circuit 52 increases the current Ib as the difference between the voltages Va and Vb increases. In the vicinity of the magnetoresistive elements M1 to M4, the magnetic field in the Y direction generated by the current Ib of the coil L acts so as to cancel the magnetic field component in the Y direction generated by the current I2 of the second bus bar 20. For this reason, a decrease in the voltage Va with respect to the voltage Vb is suppressed.

The coil drive circuit 52 has a sufficiently large gain, which is a ratio between the voltage (Va−Vb) input from the bridge circuit 51 and the current Ib output to the coil L. Therefore, the voltages Va and Vb of the bridge circuit 51 become substantially equal by the feedback operation. Thereby, in the magnetic sensors SA and SB (magnetoresistance effect elements M1 to M4), the Y-direction component of the magnetic field due to the current I2 of the second bus bar 20 and the Y-direction magnetic field due to the current Ib of the coil L are substantially equal. .

The resistor Rs is provided on the current path of the coil L. The differential amplifier 53 amplifies the voltage generated at both ends of the resistor Rs by the current Ib flowing through the coil L and outputs it as a detection signal S12. The detection signal S12 is a signal proportional to the current Ib flowing through the coil L, and is substantially proportional to the magnetic field of the coil L. The magnetic field of the coil L is controlled so as to cancel the Y direction component of the magnetic field acting on the magnetic sensors SA and SB (magnetoresistance effect elements M1 to M4) by the current I2 of the second bus bar 20, and is therefore almost proportional to the current I2. To do. Therefore, the detection signal S12 is a signal substantially proportional to the current I2.

The sensor unit 50 is formed, for example, inside a semiconductor integrated circuit, and the semiconductor integrated circuit is mounted on the substrate 60 as an electronic component. In the example of FIG. 1, the substrate 60 is fixed inside the case 70 in a posture in which the component mounting surface is perpendicular to the X direction. The case 70 is an insulating member such as resin, and is fixed to the second bus bar 20 by integral molding, for example.

In the current sensor 1 according to the present embodiment, the detected current flowing from the bus bars 101 to 102 is divided into the first bus bar 10 (

plate conductors

10A and 10B) and the second bus bar 20. The current I2 shunted to the second bus bar 20 is detected by the sensor unit 50, and a detection signal S12 indicating the detection result is generated. The ratio at which the current to be detected is divided into the first bus bar 10 and the second bus bar 20 is preset by the ratio of the resistance values of the bus bars (plate conductor 10A, plate conductor 10B, second bus bar 20). The current is set to flow evenly to each bus bar. Therefore, the detected current is obtained from the detection signal S12 generated in the sensor unit 50.

According to the current sensor 1 according to the present embodiment, the following effects can be obtained.

(1) The first bus bar 10 extending in a straight line and the bent second bus bar 20 are in contact with each other at two end portions (E11 and E12, E21 and E22). Therefore, at least a part of the second bus bar 20 bent between the two ends E21 and E22 has an extension direction (Y direction) of the first bus bar 10 extending linearly between the two ends E11 and E12. Current flows in a direction that is not parallel to). Thereby, since the magnetic field due to the current I2 flowing through at least a part of the second bus bar 20 has a component in the Y direction parallel to the extending direction of the first bus bar 10, this is detected by the magnetic sensors SA and SB. Can do. Further, since the magnetic field due to the current I1 flowing through the first bus bar 10 is perpendicular to the extending direction (Y direction) of the first bus bar 10, it does not have a component in the Y direction and is hardly detected by the magnetic sensors SA and SB. . That is, the magnetic sensors SA and SB mainly detect the magnetic field due to the current I2 flowing through the second bus bar 20, and the detection result is hardly affected by the magnetic field due to the current I1 flowing through the first bus bar 10. Therefore, the current can be detected with high accuracy based on the magnetic field of the current I2 that is shunted to the second bus bar 20. In addition, since it is not necessary to provide a magnetic shield or the like in order to reduce the influence of the magnetic field due to the current I1 that is diverted to the first bus bar 10, the number of parts can be suppressed, and the size of the device can be reduced.

(2) In a pair of locations where the pair of magnetic sensors (SA and SB) are arranged, a magnetic field component in the Y direction parallel to the extending direction of the first bus bar 10 included in the magnetic field generated by the current I2 of the second bus bar 20 There is a difference corresponding to the current I2 flowing through the second bus bar 20. In the pair of magnetic sensors (SA and SB) disposed at the pair of locations, a magnetic field in the Y direction parallel to the extending direction of the first bus bar 10 is detected, so the pair of magnetic sensors (SA and SB) The detected magnetic field has a difference corresponding to the current I2 flowing through the second bus bar 20. Therefore, the current I2 flowing through the second bus bar 20 can be detected based on the difference between the magnetic fields detected by the pair of magnetic sensors (SA and SB). In addition, since the external magnetic field from a distant noise source is substantially equal at this pair of locations, it is difficult to affect the difference between the magnetic fields detected by the pair of magnetic sensors (SA and SB). That is, the detection result of the current I2 based on the difference between the magnetic fields detected by the pair of magnetic sensors (SA and SB) is hardly affected by the external magnetic field. Therefore, the current detection accuracy can be increased.

(3) Since the second bus bar 20 has a symmetric structure with respect to the virtual plane PL, the magnetic field distribution due to the current I2 flowing through the second bus bar 20 is symmetric with respect to the virtual plane PL. In addition, the pair of places where the pair of magnetic sensors (SA and SB) are disposed are places that are plane-symmetric with respect to the virtual plane PL. Therefore, the magnetic field components in the Y direction parallel to the extending direction of the bus bar 10 out of the magnetic field due to the current I2 flowing through the second bus bar 20 are opposite to each other in the pair of locations, and the magnitudes thereof are substantially equal. Therefore, the current I2 flowing through the second bus bar 20 can be detected based on the difference between the magnetic fields in the Y direction detected by the pair of magnetic sensors (SA and SB). Further, since the

arm portions

21 and 22 are inclined with respect to the extending direction (Y direction) of the first bus bar 10, the magnetic field due to the current I2 flowing through the

arm portions

21 and 22 is extended in the extending direction of the first bus bar 10 ( (Y direction) is not parallel. Thereby, in a pair of magnetic sensors (SA and SB), since the detection sensitivity of the magnetic field with respect to the electric current I2 becomes low, it becomes possible to detect a larger electric current.

(4) Since the resistance value of the first bus bar 10 can be changed by changing the number of stacked plate-

like conductors

10A and 10B in the first bus bar 10, the shunt current between the first bus bar 10 and the second bus bar 20 can be changed. The ratio can be easily changed. Thereby, the detection range of a to-be-detected electric current can be easily changed only by removal | desorption of the plate-shaped conductor of the 1st bus bar 10, without replacing | exchanging the 2nd bus bar 20 to which the sensor part 50 was fixed. Moreover, since the 2nd bus bar 20 to which the sensor part 50 was fixed can be used in common in the various current sensors from which the detection range of an electric current differs, it becomes possible to aim at commonization of components.

(5) By making the currents flowing through the plate conductors (10A, 10B) of the first bus bar 10 equal to each other, the current flowing through one plate conductor and the current flowing through the second bus bar 20 are made equal, Since the current detection range can be changed to an integral multiple simply by changing the number of stacked plate conductors of one bus bar 10, convenience is improved.

(6) Since the planar shapes of the

plate conductors

10A and 10B viewed from the stacking direction (Z direction) are equal to each other, the first bus bar viewed from the stacking direction (Z direction) even if the number of stacked plate conductors is further increased. The size of the 10 planar shape does not change. Thereby, the enlargement of the apparatus size by expansion of the detection range of an electric current can be suppressed.

(7) Since the two end portions E21 and E22 of the second bus bar 20 are stacked on the plate conductor 10A in the same Z direction as the stacking direction, the number of stacked plate conductors in the first bus bar 10 is changed. Even so, the contact between the second bus bar 20 and the first bus bar 10 can be stably secured.

(8) Since the other bus bars (101, 102) can be overlapped and connected to the connecting portion of the second bus bar 20 and the

plate conductors

10A and 10B by the

screws

81 and 83, the number of stacked plate conductors in the first bus bar 10 The connection work does not become complicated even if the number of the lines increases.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. FIG. 6 is a diagram illustrating an example of a current sensor 1A according to the second embodiment of the present invention. A current sensor 1A shown in FIG. 6 includes a first bus bar 30 and a second bus bar 40 connected in parallel, and a sensor unit 50 having magnetic sensors SA and SB for detecting a magnetic field due to a current flowing through the second bus bar 40. Prepare.

The first bus bar 30 has a shape extending linearly between two ends E31 and E32 through which current flows, thereby forming a linear current path. In the example of FIG. 6, the extending direction of the first bus bar 30 is the Y direction.

FIG. 7 is a diagram showing a state in which the bus bars (30, 40) connected in parallel in the current sensor 1A shown in FIG. 6 are disassembled. As shown in FIG. 7, the first bus bar 30 includes two plate-

like conductors

30A and 30B. The plate-shaped

conductors

30A and 30B have a smaller size (thickness) in the X direction than a size (width) in the Z direction, and each extend linearly in the Y direction. The plate-

like conductors

30A and 30B are stacked in the X direction as shown in FIG. That is, the surface on the X1 side of the plate-like conductor 30A and the surface on the X2 side of the plate-like conductor 30B are in contact.

6 and 7, the two plate-

like conductors

30A and 30B have the same planar shape when viewed from the X direction (stacking direction). That is, the plate-shaped

conductors

30A and 30B have the same width in the Z direction and the length in the Y direction.

The second bus bar 40 has a bent shape between the two ends E41 and E42 through which a current flows, thereby forming a bent current path. The second bus bar 40 shown in FIG. 7 has two

bent portions

44 and 45, two

arm portions

41 and 42, and a base portion 43. The base portion 43 is provided between the two

bent portions

44 and 45. The arm portion 41 is provided between the bent portion 44 and the end portion E41. The arm portion 42 is provided between the bent portion 45 and the end portion E42. The

arm portions

41 and 42 extend linearly in a direction perpendicular to the extending direction (Y direction) of the first bus bar 30 and parallel to each other. In the example of FIG. 7, the

arm portions

41 and 42 extend in the Z direction, and the lengths in the extending direction are substantially equal.

Further, the second bus bar 40 shown in FIG. 7 has a bent portion 46 between the arm portion 41 and the end portion E41, and has a bent portion 47 between the arm portion 42 and the end portion E42. Both the end E41 and the end E42 extend linearly in the Y direction.

In the current sensor 1 </ b> A shown in FIG. 6, the end E <b> 31 of the first bus bar 30 and the end E <b> 41 of the second bus bar 40 are in contact with each other, and the end E <b> 32 of the first bus bar 30 and the end of the second bus bar 40 are connected. E42 comes into contact and conducts.

The two ends E41 and E42 of the second bus bar 40 are stacked on the plate conductor 30A in the same direction as the stack direction (X direction) of the

plate conductors

30A and 30B. That is, the X1 side surface of the end portion E41 of the second bus bar 40 and the X2 side surface of the end portion E31A of the plate conductor 30A are in contact with each other, and the X1 side surface of the end portion E42 of the second bus bar 40 and the plate conductor 30A. The X2 side surface of the end E32A comes into contact. The second bus bar 40 is a plate-like conductor similar to the plate-

like conductors

30A and 30B, and the size (thickness) in the X direction of the end portion E41 and the end portion E42 is smaller than the size (width) in the Z direction.

In one example, substantially equal currents flow through the plate-like conductor 30A, the plate-like conductor 30B, and the second bus bar 40. That is, these conductors have approximately the same resistance value between the two ends where current flows. In these conductors, the width in the Z direction, the thickness in the X direction, the length of the current path, the area of the contact portion, and the like are set so that substantially equal currents flow.

FIG. 8 is a diagram illustrating an example of an attached state of the current sensor 1A illustrated in FIG. 8A is a view of the X2 direction from the X1 side, and FIG. 8B is a view of the Z1 direction from the Z2 side. As shown in the example of FIG. 8, the current sensor 1A according to the present embodiment can connect the two ends E41 and E42 of the second bus bar 40 and the plate-

like conductors

30A and 30B with screws (85, 87). is there. A through hole through which a screw (85, 87) is inserted in the X direction is formed at each end of the second bus bar 40, the plate conductor 30A, and the plate conductor 30B. The second bus bar 40 has a through hole T41 at the end E41 and a through hole T42 at the end E42. The plate-like conductor 30A has a through hole T31A formed at the end E31A and a through hole T32A formed at the end E32A. The plate-like conductor 30B has a through hole T31B formed at the end E31B and a through hole T32B formed at the end E32B. Screws 85 are inserted through the through holes T41, T31A, and T31B, and screws 87 are inserted through the through holes T42, T32A, and T32B. The nuts 86 and 88 are fastened to the tips of the

screws

85 and 87 inserted through the through holes, whereby the two ends E41 and E42 of the second bus bar 40 are connected to the plate-

like conductors

30A and 30B.

As shown in FIG. 8, the

screws

85 and 87 are used to connect the bus bars 103 and 104 through which the current to be detected flows and the current sensor 1A. The end portion of the bus bar 103 has a through hole through which the screw 85 is inserted in the X direction, and is fixed between the end portion E41 of the second bus bar 40 and the nut 86. The end portion of the bus bar 104 has a through hole through which the screw 87 is inserted in the X direction, and is fixed between the end portion E42 of the second bus bar 40 and the nut 88.

The magnetic sensors SA and SB and the sensor unit 50 including the same are the same components as those of the current sensor 1 (FIGS. 1 to 5) according to the first embodiment already described. Also in the present embodiment, the sensitivity directions of the magnetic sensors SA and SB are each directed in the Y direction so as to detect a magnetic field in the Y direction parallel to the extending direction of the first bus bar 30.

The pair of locations where the pair of magnetic sensors (SA and SB) are disposed are locations where the magnetic field generated by the current of the second bus bar 40 has a magnetic field component in the Y direction parallel to the extending direction of the first bus bar 30. In addition, the magnetic field components are different from each other in accordance with the current flowing through the second bus bar 40. That is, in this pair of locations, when the current of the second bus bar 40 increases, the difference in the magnetic field component in the Y direction due to this current increases. Conversely, when the current of the second bus bar 40 is reduced, the difference in the magnetic field component in the Y direction due to this current is reduced.

In the example of FIG. 8, the pair of magnetic sensors (SA and SB) are disposed at a pair of locations that are plane-symmetric with respect to the virtual plane PL. The virtual plane PL in the present embodiment is a plane that passes through the center of the base 43 in the extending direction (Y direction) of the first bus bar 30 and is perpendicular to the extending direction (Y direction). Since the first bus bar 30 and the second bus bar 40 have a symmetric shape with respect to the virtual plane PL, the distribution of the magnetic field due to the current flowing through the first bus bar 30 and the second bus bar 40 is almost the same as the virtual plane PL. It becomes symmetric. The pair of magnetic sensors (SA and SB) detect magnetic fields due to currents flowing through the two

arm portions

41 and 42 in a pair of locations symmetrical to the virtual plane PL.

FIG. 9 is a diagram illustrating the direction of the magnetic field due to the current flowing through each bus bar (30, 40) in the current sensor 1A shown in FIG. “I3” in FIG. 9 indicates a current flowing through the first bus bar 30 (

plate conductors

30A and 30B), and “I4” indicates a current flowing through the second bus bar 40.

The magnetic field H41 generated by the current I4 flowing through the arm portion 41 at the location where the magnetic sensor SA (the magnetoresistive effect elements M1 and M2) is disposed, and the arm at the location where the magnetic sensor SB (the magnetoresistive effect elements M3 and M4) is disposed. All the magnetic fields H42 generated by the current I4 flowing through the portion 42 are parallel to the Y direction, and their directions are opposite to each other. For example, as shown in FIG. 9, when the current I4 flows from the Y2 side to the Y1 side, the magnetic field H41 faces the Y1 direction, and the magnetic field H42 faces the Y2 direction. Further, since the second bus bar 40 has a symmetrical shape with respect to the virtual plane PL, the magnetic field generated by the current I4 flowing through the second bus bar 40 is substantially symmetrical with respect to the virtual plane PL, and a pair of magnetic sensors The magnetic field strengths in (SA and SB) are almost equal. Therefore, in a pair of places where the pair of magnetic sensors (SA and SB) are disposed, the magnetic fields in the Y direction generated by the current I4 are opposite to each other, and the magnitudes thereof are substantially equal.

On the other hand, the magnetic field H3 caused by the current I3 flowing through the first bus bar 30 is perpendicular to the Y direction and has almost no magnetic field component in the Y direction. Therefore, in the magnetic sensors SA and SB (magnetoresistance effect elements M1 to M4), the magnetic field H3 due to the current I3 is hardly detected.

The output voltages Va and Vb of the bridge circuit 51 in the present embodiment change in the same manner as the bridge circuit 51 in the first embodiment already described. That is, when the current I4 flowing from the Y2 side to the Y1 side increases (or when the current I4 flowing from the Y1 side to the Y2 side decreases), the voltage Va increases and the voltage Vb decreases, and conversely, from the Y2 side to the Y1 side When the current I2 flowing to the side decreases (or the current I4 flowing from the Y1 side to the Y2 side increases), the voltage Va decreases and the voltage Vb increases. Also in the present embodiment, the feedback control is performed by the sensor unit 50 similar to that in FIG. 5, so that the current Ib of the coil L is adjusted so that the voltages Va and Vb are substantially equal, and the detection signal proportional to the current Ib. S12 is generated.

In the example of FIG. 6, as in FIG. 1, the semiconductor integrated circuit including the sensor unit 50 is mounted on the substrate 60A as an electronic component. The board 60A is fixed inside the case 70A in a posture in which the component mounting surface is perpendicular to the X direction. The case 70A is an insulating member such as a resin, and is fixed to the second bus bar 40 by, for example, integral molding.

Also in the current sensor 1A according to the present embodiment having the above-described configuration, it is possible to achieve the same effect as the current sensor 1 according to the first embodiment. In the current sensor 1A according to the present embodiment, since the

arm portions

41 and 42 are perpendicular to the extending direction (Y direction) of the first bus bar 30, the magnetic field due to the current I4 flowing through the

arm portions

41 and 42 is The first bus bar 30 is substantially parallel to the extending direction (Y direction). Thereby, in a pair of magnetic sensors (SA and SB), since the detection sensitivity of the magnetic field with respect to the electric current I4 becomes high, a smaller electric current can be detected.

Although some embodiments of the present invention have been described, the present invention is not limited to these embodiments and includes various variations.

For example, in the above-described embodiment, the first bus bar (10, 30) includes two plate conductors (10A and 10B, 30A and 30B), but in other embodiments of the present invention, three or more plates are used. A shaped conductor may be included. Further, when the detected current is small, the first bus bar may be omitted, and the current may be detected using only the second bus bar.

In the embodiment described above, a half bridge circuit in which two magnetoresistive elements are connected in series to each of a pair of magnetic sensors (SA and SB) is used, but the present invention is not limited to this example. In another embodiment of the present invention, one magnetoresistive effect element is used for each of a pair of magnetic sensors arranged at a pair of locations, and the relative difference between the resistance values (the magnetic field difference at the pair of locations is calculated). A detection signal corresponding to the current of the second bus bar may be generated. Further, the magnetoelectric conversion element used for the magnetic sensor is not limited to the magnetoresistive effect element, and other magnetoelectric conversion elements such as a Hall element may be used.

In the embodiment described above, the coil current is feedback-controlled so that the magnetic field due to the current of the second bus bar is canceled by the magnetic field due to the coil current, and the detection result of the detected current is obtained from the current of the coil. Is not limited to this example. In another embodiment of the present invention, the detection result of the detected current may be directly obtained based on the signal of the magnetic sensor corresponding to the magnetic field generated by the current of the second bus bar.

DESCRIPTION OF SYMBOLS 1,1A ... Current sensor, 10 ... 1st bus bar, 10A, 10B ... Plate-shaped conductor, 20 ... 2nd bus bar, 21, 22 ... Arm part, 23-25 ... Bending part, 30 ... 1st bus bar, 30A, 30B ... Plate-like conductor, 40 ... Second bus bar, 41, 42 ... Arm part, 43 ... Base part, 44-47 ... Bending part, 50 ... Sensor part, 51 ... Bridge circuit, 52 ... Coil drive circuit, 53 ... Differential amplifier , 60, 60A ... substrate, 70, 70A ... case, SA, SB ... magnetic sensor, M1-M4 ... magnetoresistive effect element, 81, 83, 85, 87 ... screw, 82, 84, 86, 88 ... nut, 101 ~ 104 ... busbar, E11, E12, E21, E22, E31, E32, E41, E42 ... end, T11A, T11B, T12A, T12B, T21, T22, T31A, T31B, T32A, T32B T41, T42 ... through hole, PL ... virtual plane, L ... coil

Claims

A first bus bar extending linearly between two ends through which current flows;
A second bus bar bent between two ends through which current flows;
A magnetic sensor for detecting a magnetic field caused by a current flowing through the second bus bar;
The one end of the first bus bar and the one end of the second bus bar are in contact with each other and are electrically connected, and the other end of the first bus bar and the other end of the second bus bar. And are in contact with each other,
The magnetic sensor detects a magnetic field in a direction parallel to the extending direction of the first bus bar;
Current sensor.
A pair of magnetic sensors arranged at a pair of locations,
The pair of places is a place where the magnetic field generated by the current of the second bus bar has a magnetic field component parallel to the extending direction of the first bus bar, and the magnetic field component of each other is a current flowing through the second bus bar. A place with a corresponding difference,
The current sensor according to claim 1.
The second bus bar is
Bends,
Extending from the bent portion to the two end portions linearly in a direction inclined with respect to the extending direction of the first bus bar, and having two arm portions having the same length.
The pair of magnetic sensors are disposed in a pair of locations that are symmetrical with respect to a virtual plane that passes through the bent portion and is perpendicular to the extending direction of the first bus bar, and currents flowing through the two arm portions. Detect the magnetic field by
The current sensor according to claim 2.
The second bus bar is
Two bends,
Provided between the one bent portion and the one end portion, and between the other bent portion and the other end portion, and in a direction perpendicular to the extending direction of the first bus bar; Two arms extending linearly in directions parallel to each other;
A base provided between the two bent portions,
The pair of magnetic sensors are disposed at a pair of locations that are plane-symmetric with respect to a virtual plane that passes through the center of the base in the extending direction of the first bus bar and is perpendicular to the extending direction. Detect the magnetic field due to the current flowing in the arm,
The current sensor according to claim 2.
Each of the first bus bars extends linearly in the extending direction, and includes a plurality of plate-like conductors stacked in a direction perpendicular to the extending direction.
The current sensor according to any one of claims 1 to 4.
The currents flowing through each of the plurality of plate conductors are equal to each other,
The current flowing in one plate-like conductor is equal to the current flowing in the second bus bar;
The current sensor according to claim 5.
The plurality of plate conductors have the same planar shape as seen from the stacking direction,
The current sensor according to claim 5 or 6.
The two ends of the second bus bar are stacked on the plate conductor in the same direction as the stacking direction;
The current sensor according to any one of claims 5 to 7.
The two end portions of the second bus bar and the plurality of plate-like conductors can be connected by screws;
A through hole through which the screw is inserted in a direction parallel to the stacking direction is formed in the two end portions of the second bus bar,
A through-hole through which the screw is inserted in a direction parallel to the stacking direction is formed at two ends of the plate-like conductor,
The current sensor according to claim 8.